Strategies for the environmental recovery of abandoned mining areas

Abandoned mining areas are a clear example of the failure of the different administrations to solve the environmental problems they pose, due to the lack of unified legislation and management and the activity of geological processes. It is therefore important to have a clear vision of the environmental problems that occur and the possible actions to solve them.

The Sierra Minera (Cartagena, SE Spain) presents situations of risk of soil contamination that coincide with those areas with the highest content of soluble and/or bioavailable PTEs (potentially toxic elements) for the health of people and ecosystems, especially in those sites of concentration of polluting sources (flotation mud pools and heterogeneous dumps), with a very fine texture. These areas present numerous points with an urgent need for risk management due to the possible mobilization in different environmental conditions of arsenic and heavy metals, with a control of both soluble and particulate dispersion. Special interest presents arsenic mobilisation in an acidic environment together with reducing situations and the presence of organic matter (waterlogged marshes).

The recovery technologies to be applied in the Sierra Minera require a great diversity of techniques, depending on the uses of the land. In the contamination foci it is necessary to carry out actions with containment, stabilisation and solidification technologies in situ. Phytoremediation techniques, given the high content of PTEs present, may not all be appropriate in the different situations. Phytoextraction should only be applied in areas with low concentrations of PTEs, and by plants that do not transfer to their aerial part, to avoid the risk of ingestion by animals. Phytostabilisation will be important in combined techniques, in order to ensure that contaminants are not transferred to the environment, and by non-accumulating plants in the aerial part. Wetlands can be a complementary solution to the projects developed at the heading of wadis, providing a double purpose, natural attenuation of contamination and lamination of turbulence and floods.

A generic overview is given of the most important regeneration approaches from a geochemical point of view, without going into structural solutions, selecting those technologies that are most suitable to the environment in which they are located, trying to imitate natural attenuation processes and using eco-efficient and sustainable materials.